Early antimicrobial therapy and clinical outcomes of left-sided Enterococcus faecalis endocarditis: a NIDUS registry study

Abstract Purpose Antimicrobial therapy of Enterococcus faecalis endocarditis treatment is challenged by high intrinsic resistance and relapse rates. Knowledge on practice patterns is warranted. We aimed to describe early-phase monotherapy and combination therapy use in E. faecalis endocarditis treatment. Methods This retrospective, nationwide cohort study was conducted in Denmark between 2016 and 2021. All patients with left-sided E. faecalis endocarditis were derived from the NatIonal Danish endocarditis stUdieS registry (NIDUS). Antimicrobial therapy during the first 10 days was compared between monotherapy and combination therapy. The groups were compared by in-hospital mortality, acute kidney injury and surgery with logistic regression and 6-month relapse and recurrence rate and 6-month mortality rate with Kaplan-Meier estimates and multivariable cox regression. Results We included 392 patients, 59(15.1%) received monotherapy and 333 (84.9%) combination therapy. Patients in monotherapy were older (median 79.3 versus 76.0 years) and had more comorbidities. Monotherapy comprised ampicillin (74.6%), vancomycin (16.9%) and penicillin (6.8%). Among combination regimens the most frequent were ampicillin +gentamicin (65.4%), ampicillin + linezolid (6.6%) and ampicillin + ceftriaxone (5.1%). Surgical rates were comparable. Acute kidney injury during admission occurred in 20.7% versus 16.6% patients. No significant difference in relapse (5.9% versus 8.5%) or recurrence rates (5.4% versus 6.8%) was found. Similar in-hospital mortality (13.8% vs. 11.9%) and 6-month mortality rates were seen in the monotherapy and combination therapy groups. Conclusion The most common treatment of E. faecalis endocarditis was combination therapy, however certain selected patients were treated with monotherapy with similar outcomes. Use of monotherapy remains controversial and would need testing in a controlled randomized setting.